This present invention concerns a drainage geocomposite applied, for example, to drainage of the ground or of civil engineering creations, and its method of manufacture.
Previous designs have included various geocomposite materials intended for drainage of the ground or of civil engineering creations. Such materials are composed of draining geotextiles that frequently include a geo-spacer with the whole maintained between two sheets of filtering geotextiles. In this present case, the geo-spacer is composed of either girdled and perforated tubes, or of helical springs or of an tube equipped with fins, thus providing continuous passages for drainage of the interstitial water.
The geocomposite can be composed of a filtration sheet and a drainage sheet, with the geo-spacer most often located in a gusset between the two sheets. The sheets, both drainage and filtration, are created from non-woven fibres and are then joined together either by glueing or by lines of stitching that run the length of the geo-spacers in order to create the geocomposite.
Since assembly by glueing can alter the filtration qualities of the geomaterial, certain geocomposites are assembled by means of the needlepunching method.
A variant of this method is described in patent U.S. Pat. No. 5,475,904, where this method includes several stages, namely a stage for assembly of two compounds (a drainage sheet and a filtration sheet, for example), a stage in which the compounds are then conveyed to the needlepunching machine, and then a stage in which they are joined together. A space is created between the two compounds in order to be able to insert other materials after needlepunching, in particular liquids which will then be hardened.
Patents FR 2 746 424 and EP 0 962 754 describe geotextiles that have at least one filtration sheet and at least one drainage sheet, assembled by this needlepunching method. In the case of patent EP 0 962 754, a network of electrodes is placed between the two sheets. For patent FR 2 746 424, these are drains perforated uniformly all around periphery of the rings that are inserted between the two sheets.
Such creations nevertheless have certain drawbacks. In fact, the geomaterials created using the aforementioned techniques can have a low resistance to internal shear forces thereby limiting their use to flat or slightly sloping surfaces. In addition, the creations in which the sheets are glued or stitched together do not result in a geomaterial with a uniform and constant porosity, since the inter-sheet connections are not homogeneous, in particular regarding the stitching or the glueing. The multiplication of the stages in certain cases further complicates these techniques. Finally, the uniform perforation of the drains does not allow removal of the interstitial water when the materials have been subjected to compressive forces.